1. Field of the Invention
The invention relates to an anode for batch anodizing of a length of metallic conductor wire. More specifically, the invention relates to an anode for generating an electrically insulating oxide layer on the surface of a wire length of electric conductor wire of metal by anodizing, wherein the anode is immersed into an electrolyte. The invention also relates to a process for batch anodizing of a wire length of metallic conductor wire, in which such an anode is utilized, an insulated conductor wire with an electrically insulating surface layer by batch anodizing according to the invented anodizing process, and an electric device having one or more such insulated conductor wires which have been provided with an electrically insulating surface layer by batch anodizing.
2. Discussion of the Background
An electric device such as a cable, a transformer, a generator, a motor, etc., has at least one current carrying and voltage-carrying metallic body, hereinafter in this document referred to as a conductor. Certain high-voltage electric devices include conductors which have a large number of conductor wires of a more slender dimension, referred to in this document as strands. The strands are composed, for example laid, into parts of strands, windings or coils in generators and other electric machines. The voltage difference between the laid strands is low but the laid strands are still often insulated relative to one another.
According to the prior art, single-wire conductor wires which, as strands, are laid into coarser conductors, included in high-voltage devices, are insulated preferably by organic insulating materials, such as thermoplastic resins, waxes or varnishes. However, organic insulating materials have a poor capacity to withstand influence in severe environments. For example, they have a low temperature resistance and they must often be applied in relatively thick layers. The organic insulations also give rise to drawbacks and costs when recycling/recovering consumed or rejected conductor material since they have to be taken care of or destructed separately from the metallic conductor wire. For use in severe environments such as at high temperatures, under vacuum, in chemically aggressive environments or in environments involving a high fire hazard, it is known to use inorganic insulating materials such as insulating materials based on glass fibre or mica, which are usually wound onto the conductor wire. Further, it is known to insulate aluminum wire or aluminum-coated copper wire with a surface layer of aluminum oxide by anodic oxidation, anodizing. To obtain an oxide layer with a suitable structure and adhesion for the use described above, a treatment cycle is required which cannot be realized by way of a continuous electrochemical process but requires a batch process. A problem in this connection is to arrange a wire of a wire length sufficient for a coil- in an electric high-voltage device. The wire length in a coil usually amounts to between a few two hundred meters and a few kilometers. The wire must in its entirety be connected to the positive pole of a current source in such a way that the potential difference is minimized over the long wire length. The wire, which preferably has a diameter of 1 to 5 mm, must usually be supported and kept in such a way that essentially the whole surface may be anodized.